Friction weld coaxial connector and interconnection method

ABSTRACT

A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by friction welding is provided with a monolithic connector body with a bore. A sidewall of the bore is provided with an inward annular projection angled toward a cable end of the bore. A sidewall of the inward annular projection and the sidewall of the bore form an annular friction groove open to a cable end of the bore. The annular friction groove is dimensioned with a taper at a connector end of the friction groove less than a thickness of a leading end of the outer conductor. The taper provides an annular material chamber between the leading end of the outer conductor, when seated in the friction groove, and the connector end of the friction groove.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly owned co-pending U.S. Utility patent application Ser. No. 12/951,558, titled “Laser Weld Coaxial Connector and Interconnection Method”, filed Sep. 14, 2009 by Ronald A. Vaccaro, Kendrick Van Swearingen, James P. Fleming, James J. Wlos and Nahid Islam, currently pending and hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

This invention relates to electrical cable connectors. More particularly, the invention relates to a coaxial cable connector interconnectable via friction welding.

2. Description of Related Art

Coaxial cable connectors are used, for example, in communication systems requiring a high level of precision and reliability.

To create a secure mechanical and optimized electrical interconnection between the cable and the connector, it is desirable to have generally uniform, circumferential contact between a leading edge of the coaxial cable outer conductor and the connector body. A flared end of the outer conductor may be clamped against an annular wedge surface of the connector body via a coupling body. Representative of this technology is commonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz.

Although this type of connector is typically removable/re-useable, manufacturing and installation is complicated by the multiple separate internal elements required, interconnecting threads and related environmental seals.

Connectors configured for permanent interconnection via solder and/or adhesive interconnection are also well known in the art. Representative of this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep. 8, 1998 to Bufanda et al. However, solder and/or adhesive interconnections may be difficult to apply with high levels of quality control, resulting in interconnections that may be less than satisfactory, for example when exposed to vibration and/or corrosion over time.

Competition in the coaxial cable connector market has focused attention on improving electrical performance and long term reliability of the cable to connector interconnection. Further, reduction of overall costs, including materials, training and installation costs, is a significant factor for commercial success.

Therefore, it is an object of the invention to provide a coaxial connector and method of interconnection that overcomes deficiencies in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, where like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.

FIG. 1 is a schematic external isometric view of an exemplary embodiment of a coaxial connector installed upon a coaxial cable with a coupling nut spaced away from the connector along the cable for connector-to-cable interconnection.

FIG. 2 is a schematic isometric view of the coaxial connector of FIG. 1 installed upon a coaxial cable, with the coupling nut seated upon the coaxial connector.

FIG. 3 is a schematic isometric view of the coaxial connector of FIG. 1.

FIG. 4 is a schematic cross section side view of FIG. 2.

FIG. 5 is an enlarged view of area A of FIG. 4.

FIG. 6 is a schematic exploded isometric partial cut-away view of the connector and cable of FIG. 1.

FIG. 7 is a schematic isometric partial cut-away view of the connector body of FIG. 5.

FIG. 8 is a schematic isometric view of an alternative connector body with notches on a flange of the connector body.

FIG. 9 is a schematic isometric view of an alternative connector body with longitudinal knurls on the connector body outer diameter.

FIG. 10 is a schematic isometric cut-away view of the overbody of FIG. 5.

FIG. 11 is an enlarged view of area B of FIG. 4.

FIG. 12 is a schematic cross section side view of an alternative overbody with corrugation on an inner diameter of the cable end.

FIG. 13 is a schematic cross section side view of an alternative overbody with a stepped surface on an inner diameter of the cable end.

FIG. 14 is a schematic cross section side view of a coaxial connector embodiment with an inner conductor end cap.

DETAILED DESCRIPTION

Aluminum has been applied as a cost-effective alternative to copper for the conductors in coaxial cables. However, aluminum oxide surface coatings quickly form upon air-exposed aluminum surfaces. These aluminum oxide surface coatings may degrade traditional mechanical, solder and/or conductive adhesive interconnections.

The inventors have recognized that increasing acceptance of coaxial cable with solid outer conductors of aluminum and/or aluminum alloy enables connectors configured for interconnection via friction welding between the outer conductor and a connector body which may also be cost effectively provided, for example, formed from aluminum and/or aluminum alloy.

An exemplary embodiment of a friction weldable coaxial connector 2 is demonstrated in FIGS. 1-4. As best shown in FIG. 4, a unitary connector body 4 is provided with a bore 6 dimensioned to receive the outer conductor 8 of a coaxial cable 9 therein. An inward projecting shoulder 10 angled toward a cable end 12 of the connector body 4 forms an annular friction groove 14 open to the cable end 12. As best shown in FIG. 5, the friction groove 14 is dimensioned to receive a leading edge of the outer conductor 8 therein, a thickness of the outer conductor 8 preventing the outer conductor 8 from initially bottoming in the friction groove 14, forming an annular material chamber 16 between the leading edge of the outer conductor 8 and the bottom of the friction groove 14, when the outer conductor 8 is initially seated within the friction groove 14.

One skilled in the art will appreciate that connector end 18 and cable end 12 are applied herein as identifiers for respective ends of both the connector and also of discrete elements of the connector described herein, to identify same and their respective interconnecting surfaces according to their alignment along a longitudinal axis of the connector between a connector end 18 and a cable end 12.

The bore sidewall 20 may be diametrically dimensioned to create a friction portion 22 proximate the friction groove 14. The friction portion 22 creates additional interference between the bore sidewall 20 and the outer diameter of the outer conductor 8, to increase friction during friction welding.

Prior to interconnection via friction welding, also known as spin welding, the cable end 12 may be prepared, as best shown in FIG. 6, by cutting the cable 9 so that the inner conductor 24 extends from the outer conductor 8. Also, dielectric material 26 between the inner conductor 24 and outer conductor 8 may be stripped back and a length of the outer jacket 28 removed to expose desired lengths of each, including a sacrificial portion of the outer conductor 8 which is consumed during the friction welding process.

To initiate friction welding, the connector body 4 is rotated with respect to the outer conductor 8 during seating of the leading edge of the outer conductor 8 within the friction portion 22 and into the friction groove 14, under longitudinal pressure. During rotation, for example at a speed of 250 to 500 revolutions per minute, the friction between the leading edge and/or outer diameter of the outer conductor 8 and the friction portion 22 and/or friction groove 14 of the bore 6 generate sufficient heat to soften the leading edge and/or localized adjacent portions of the outer conductor 8 and connector body 4, forging them together as the sacrificial portion of the outer conductor 8 forms a plastic weld bead that flows into the material chamber 16 to fuse the outer conductor 8 and connector body 4 together.

Because the localized abrasion of the friction welding process can break up any aluminum oxide surface coatings in the immediate weld area, no additional care may be required with respect to removing or otherwise managing the presence of aluminum oxide on the interconnection surfaces.

An overbody 30, as shown for example in FIG. 10, may be applied to the connector body 4 as an overmolding of polymeric material. The overbody 30 increases cable to connector torsion and pull resistance. The overbody 30 may also provide connection interface structure at the connector end 18 and further reinforcing support at the cable end 12, enabling significant reductions in the size of the connector body 4, thereby reducing overall material costs.

Depending upon the applied connection interface 31, demonstrated in the exemplary embodiments herein as a standard 7/16 DIN interface, the overbody 30 may be provided with an overbody flange 32 and longitudinal support ridges 34 for a coupling nut 36. The coupling nut 36 is retained upon the support ridges 34 at the connector end 18 by an overbody flange 32 and at the cable end 12 by a retention spur 38 provided on at least one of the support ridges 34. The retention spur 38 may be angled toward the connector end 18, allowing the coupling nut 36 to be placed over the cable 9 initially spaced away from the coaxial connector 2 during interconnection (see FIG. 1), but then allowing the coupling nut 36 to be passed over the retention spur 38 and onto the support ridges 34 from the cable end 12, to be thereafter retained upon the support ridges 34 by the retention spur(s) 38 (see FIG. 2) in close proximity to the connector interface 31 for connector to connector mating. The support ridges 34 reduce polymeric material requirements of the overbody 30 while providing lateral strength to the connector/interconnection 2 as well as alignment and retention of the coupling nut 36.

The overbody 30 may also extend from the connector end 18 of the connector body 4 to provide portions of the selected connector interface 31, such as an alignment cylinder 39 of the 7/16 DIN interface, further reducing metal material requirements of the connector body 4.

The overbody flange 32 may be securely keyed to a connector body flange 40 of the connector body 4 and thereby with the connector body 4 via one or more interlock apertures 42 such as holes, longitudinal knurls 43, grooves, notches 45 or the like provided in the connector body flange 40 and/or outer diameter of the connector body 4, as demonstrated in FIGS. 7-9. Thereby, as the polymeric material of the overbody 30 flows into the interlock apertures 42 during overmolding, upon curing the overbody 30, for example as shown in FIG. 10, is permanently coupled to and rotationally interlocked with the connector body 4.

As best shown in FIG. 11, the cable end 12 of the overbody 30 may be dimensioned with an inner diameter friction surface 44 proximate that of the coaxial cable outer jacket 28, enabling polymeric friction welding between the overbody 30 and the outer jacket 28, as the connector body 4 and outer conductor, thereby eliminating the need for environmental seals at the cable end 12 of the connector/cable interconnection. During friction welding, the coaxial connector 2 is rotated with respect to the cable 9. Friction between the friction surface 44 and the outer diameter of the outer jacket 28 heats the respective surfaces to a point where they begin to soften and intermingle, sealing them against one another. To provide enhanced friction and allow voids for excess flow due to friction displacement and add key locking for additional strength, the outer jacket 28 and/or the inner diameter of the overbody 30 may be provided as a series of spaced apart annular peaks of a contour pattern such as a corrugation 46, as shown for example in FIG. 12, or a stepped surface 48, as shown for example in FIG. 13. Alternatively, the overbody 30 may be sealed against the outer jacket 28 with an adhesive/sealant or may be overmolded upon the connector body 4 after interconnection with the outer conductor 8, the heat of the injected polymeric material bonding the overbody 30 with and/or sealing against the outer jacket 28.

The inner conductor 24 extending from the prepared end of the coaxial cable 9 may be selected to pass through to the connector end 18 as a portion of the selected connection interface 31, for example as shown in FIG. 4. If the selected coaxial cable 9 has an inner conductor 24 that has a larger diameter than the inner conductor portion of the selected connector interface 31, the inner conductor 24 may be ground at the connector end 18 to the required diameter.

Although a direct pass through inner conductor 24 advantageously eliminates interconnections, for example with the spring basket of a traditional coaxial connector inner contact, such may introduce electrical performance degradation such as PIM. Where the inner conductor 24 is also aluminum material some applications may require a non-aluminum material connection point at the inner contact/inner conductor of the connection interface 31. As shown for example in FIG. 14, a center cap 50, for example formed from a metal such as brass or other desired metal, may be applied to the end of the inner conductor 24, also by laser or friction welding. To apply the center cap 50, the end of the inner conductor 24 is ground to provide a pin corresponding to the selected socket geometry of the center cap 50. To allow material inter-flow during welding attachment, the socket geometry of the center cap 50 and or the end of the inner conductor 24 may be formed to provide material gaps as described with respect to the material chamber 16 described herein above.

One skilled in the art will appreciate that the connector and interconnection method disclosed has significant material cost efficiencies and provides a permanently sealed interconnection with reduced size and/or weight requirements.

Table of Parts 2 coaxial connector 4 connector body 6 bore 8 outer conductor 9 cable 10 shoulder 12 cable end 14 friction groove 16 material chamber 18 connector end 20 bore sidewall 22 friction portion 24 inner conductor 26 dielectric material 28 outer jacket 30 overbody 31 connection interface 32 overbody flange 34 support ridge 36 coupling nut 38 retention spur 39 alignment cylinder 40 connector body flange 42 interlock aperture 43 longitudinal knurl 44 friction surface 45 notch 46 corrugation 48 stepped surface 50 center cap

Where in the foregoing description reference has been made to materials, ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims. 

1. A coaxial connector for interconnection with a coaxial cable with a solid outer conductor, comprising: a monolithic connector body with a bore; a sidewall of the bore provided with an inward annular projection angled toward a cable end of the bore; a sidewall of the inward annular projection and the sidewall of the bore forming an annular friction groove open to a cable end of the bore; the annular friction groove dimensioned with a taper at a connector end of the friction groove less than a thickness of a leading end of the outer conductor; the taper providing an annular material chamber between the leading end of the outer conductor, when seated in the friction groove, and the connector end of the friction groove.
 2. The connector of claim 1, wherein the inward annular projection is located proximate a connector end of the bore.
 3. The connector of claim 1, wherein a diameter of the bore proximate the inward annular projection decreases to an interference fit with an outer diameter of the outer conductor.
 4. The connector of claim 1, further including an overbody of polymeric material on an outer diameter of the connector body.
 5. The connector of claim 4, wherein the overbody includes an alignment cylinder of a connector interface at a connector end of the connector.
 6. The connector of claim 4, wherein the overbody includes a plurality of longitudinal support ridges extending from an outer diameter of the overbody to less than an inner diameter of a coupling nut dimensioned to seat upon the support ridges.
 7. The connector of claim 6, wherein the coupling nut is retained on the support ridges between a flange of the overbody and an outward extending retention spur proximate a cable end of at least one of the support ridges.
 8. The connector of claim 4, wherein the overbody extends from the cable end of the connector body, an inner diameter of the overbody extending from the cable end of the connector body provided as a friction surface with an interference fit upon an outer diameter of a jacket of the coaxial cable.
 9. The connector of claim 8, wherein the friction surface is provided as a series of spaced apart annular peaks of a contour pattern of the inner diameter of the overbody.
 10. The connector of claim 4, further including a rotational interlock between the overbody and the connector body.
 11. The connector of claim 10, wherein the rotational interlock is a plurality of interlock apertures provided in a connector body flange protruding from an outer diameter of the connector body.
 12. A method for interconnecting a coaxial connector with a solid outer conductor coaxial cable, comprising the steps of: providing a monolithic connector body with a bore; a sidewall of the bore provided with an inward annular projection angled toward a cable end of the bore; a sidewall of the inward annular projection and the sidewall of the bore forming an annular friction groove open to a cable end of the bore; inserting a leading end of the coaxial cable into the bore, until a leading end of the solid outer conductor seats within the friction groove; rotating the connector body about a longitudinal axis of the leading end of the coaxial cable, while applying longitudinal force driving the friction groove against the leading end of the outer conductor.
 13. The method of claim 12, wherein the outer conductor and the connector body are each one of aluminum and aluminum alloy material.
 14. The method of claim 12, wherein the friction groove is provided with an annular material chamber at a connector end of the friction groove.
 15. The method of claim 12, wherein the rotation and longitudinal force are applied until heat sufficient to melt the leading end of the outer conductor is generated.
 16. The method of claim 12, wherein the rotation and longitudinal force generate a friction weld between the outer conductor and the connector body.
 17. The method of claim 12, further including the step of overmolding the connector body attached to the end of the coaxial cable with a polymeric overbody.
 18. The method of claim 12, further including the steps of preparing the leading end of the cable end prior to insertion into the bore by removing a portion of the outer conductor so that an inner conductor extends therefrom, removing a portion of a dielectric material between the inner conductor and the outer conductor such that when the leading edge of the outer conductor contacts the inward annular projection, the friction groove does not contact the dielectric material; and stripping back a portion of a jacket from the outer conductor.
 19. The method of claim 12, further including providing an overbody of polymeric material upon an outer diameter of the connector body, the overbody extending from the cable end of the connector body, an inner diameter of the overbody extending from the cable end of the connector body provided as a friction surface dimensioned for an interference fit upon an outer diameter of a jacket of the coaxial cable.
 20. The method of claim 19, wherein the rotation and longitudinal force form a friction weld between the outer conductor and the connector body and between the overbody and the jacket of the coaxial cable. 